The present invention pertains to the field of pathology and to a method for detection of products of systemic hemolysis and hepato-biliary disorders, namely porphyrins and porphyrin metabolites, deposited in human dentition. In particular, the invention is directed to providing a clinical method of screening patients for the occurrence of sickle cell disease in a manner which can be utilized in conjunction with routine dental examination.
The sickle cell disease, which encompasses the sickle cell trait and anemia associated therewith, is well known and is characteristically associated with red blood cells having an abnormal "sickle" shape. It is also well known that hemolysis of red blood cells is associated with sickle cell disease and occurs as a result thereof. As a consequence of hemolysis, porphyrins and porphyrin metabolites, in particular bilirubin and biliverdin, are released into the blood stream. While other pathological conditions can also cause hemolysis, for purposes of the invention it is sufficient to note that hemolysis, and the accompanying release of porphyrins and porphyrin metabolites, is well documented as an inherent characteristic associated with and indicative of sickle cell disease.
Porphyrins comprise a portion of hemoglobin, the major constituent of human red blood cells. Hemolysis involves the destruction of the red blood cell, which results in liberation of porphyrins in the blood stream. These porphyrins may subsequently be further broken down to bilirubin and biliverdin metabolites. It is known that porphyrins, as well as these porphyrin metabolites, will be absorbed and accumulate in the dentine of the teeth, as they are formed and calcified in the developing infant and child. Since sickle cell traits are passed genetically, porphyrins and porphyrin metabolites will be found in the patients possessing sickle cell disease and accumulate permanently in the dentition, as it develops.
Porphyrins are normally produced in the healthy body in connection with production of red blood cells, in which structures they are isolated and known as "hemato-porphyrins". A pathological condition termed porphyria is known in which the mechanism for production of hemato-porphyrins becomes uncontrolled and excess porphyrins are produced. These porphirins enter the blood stream and collect in certain parts of the body, depending upon the specific pathological condition experienced. In one rare type of porphyria, known as "congenital erythropoietic porphyria", high levels of porphyrins collect in the teeth. However, both as is recognized in the medical art and for purposes of this invention, the conditions involving porphyria and hemolysis associated with the sickle cell disease are different and distinct pathologies.
Likewise, the accumulations of porphyrins and porphyrin metabolites in various parts of the body, including the teeth, are different and distinguishable, not only in degree, but also as regards the levels which can accumulate and the fact that they have different systemic clinical manifestations. For example, congenital erythropoietic porphyria is readily distinguishable due to abnormal facial hair growth and extensive scarring on the skin, as well as a yellowish to reddish-brown discoloration of the teeth.
In the prior art, screening tests for the detection of sickle cell disease, as well as hepato-biliary disorders, have required that a specimen be obtained from the patient. Usually, either blood or urine specimens were obtained and examined either for the characteristically shaped sickle cells, in the case of a blood specimen, or the presence of porphyrins or porphyrin metabolites, in the case of urine analysis.
One significant disadvantage of these prior art techniques stems from the necessity of obtaining a specimen from the patient who, of course, must present himself or herself for submission of the specimen. Experience has shown that it can be difficult to successfully communicate to those individuals who may genetically be candidates for the sickle cell trait that it is necessary to submit to a special examination.
It is a particular advantage of the present invention that a method is provided whereby individuals, who genetically may be candidates for the sickle cell disease, can be clinically screened for its occurrence in conjunction with a routine dental examination. Since routine dental examinations are now widely available to most, if not all children, the present invention provides a method whereby the sickle cell traits can be identified much earlier then they might otherwise be detected later in life, when the anemic symptoms begin to manifest themselves outwardly in a more advanced stage of the disorder.
It is well known that porphyrins fluoresce with a characteristic red color, even in very low concentrations, under ultra-violet light, as set forth in Porphyrins, by A. Vannotti, Hilger & Watts Ltd., London, 1954, pages 18, 19, 24, 25, 72 and 73. Porphyrin metabolites, namely bilirubin and biliverdin, which result from the breakdown of porphyrin, are also known to fluoresce in the visual green range, usually about 500 nanometers (nm), when in the presence of zinc.
While the teeth are normally free from the presence or accumulation of porphyrins or the porphyrin metabolites, it is known that if porphyrin and its metabolites are present in the blood stream during the time the teeth form, they will be absorbed and accumulate in the dentine of teeth. As observed and reported by Williams et al, Hematology, p 452-453, McGraw-Hill, New York, 1972, discoloration of the teeth and emission of characteristic red fluorescence, under ultra-violet light, is a known phenomena associated with only the aforementioned congenital erythropoietic type of porphyria.
As indicated by Vannotti et al, the accumulation of porphyrins resulting from hemolysis in the dentine can be detected upon exposure of the tooth dentine to ultra-violet light. However, these observations were made with regard to in vitro study of tooth dentine, which lies inside the tooth enamel. Accordingly, there is no teaching or suggestion in the prior art that a clinical method could be developed for in vivo detection of the presence of porphyrins or porphyrin metabolites resulting from hemolysis or sickle cell disease.
Accordingly, the present invention provides a novel method for clinically screening for the presence of sickle cell disease or occurrence of hemolysis, through clinical in vivo examination of the tooth enamel. As a result, a highly advantageous advance in the art has been achieved, in that a method for detection of porphyrins or porphyrin metabolites is provided which does not require removal of a specimen from the patient, nor in vitro inspection of the tooth.